Category: Publications

Abstract

Biology has always motivated engineers to come up with efficient and reliable machines to move in complex environments. The dexterity, softness, and body compliance of natural system such as cephalopods or caterpillars have inspired robotic engineers to incorporate soft, deformable materials such as gels and elastomers into their designs. Hence, the inception of soft robots shifts the paradigm and trends in robotics, which could potentially revolutionize health care, human–robot interaction, field exploration, rehabilitation, and related applications. Throughout this review article, we have restricted our discussion to the applications of soft robots in biomedical domains exclusively and the perennial challenges faced therein.

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Soft robotics with compliance and… (PDF Download Available). Available from: [accessed May 30 2018].

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Soft-bodied robots, due to their intrinsic compliance, have shown great potential for operating within unstructured environment and interacting with unknown objects. This paper deals with automatic design and fabrication of soft robots. From a structure point of view, we synthesize a soft cable-driven gripper by recasting its mechanical design as a topology optimization problem. Building on previous work on compliant mechanism optimization, we model the interactions between the gripper and objects more practically, in form of pressure loadings and friction tractions, and further, we investigate how the interaction uncertainties affect the optimization solution by varying the contact location and area. The optimized soft fingers were 3D printed and then assembled to build a gripper. The experiments show that the gripper can handle a large range of unknown objects of different shapes and weights (up to 1 kilogram), with different grasping modes. This work represents an important step toward leveraging the full potential of the freeform design space to generate novel soft-bodied robots.

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This paper presents the development of a novel 2D Fiber Bragg Grating (FBG)-based micro-force sensing design for detection of catheter tip-tissue interaction forces. A miniature and symmetrical force-sensitive flexure-based catheter distal sensor has been prototyped, and four optical fibers inscribed with one FBG element each have been mounted on it for force and temperature decoupling and detection. The axial property of the tightly suspended fiber configuration has been utilized with a pre-tensioned force, and the embedded FBG element can be stretched and compressed to sense the force-induced and temperature-caused strain variations. The proposed configuration can achieve an improved resolution and sensitivity than the light intensity modulation-based approaches, and avoid the limitations closely associated with the commonly direct FBG-pasting methods such as chirping failure and low repeatability. Finite element modeling (FEM)-based simulation has been implemented to investigate the flexure performance and improve the design. The decoupling approach has been proposed based on the simulation results and implemented to separate and determine the force and temperature. The force-sensing flexure prototype has been calibrated to achieve a resolution of around 4.6mN within the measurement range of 0~3.5 N. Both static calibration experiments and in-vitro dynamic experiments have been performed to prove the feasibility of the proposed design. The decoupling capacity of force and temperature will benefit its broad implementations in generalized intravascular catherization procedures.

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Magnetic resonance imaging (MRI) is beneficial for imaging-guided procedures because it provides higher resolution images and better soft tissue contrast than computed tomography (CT), ultrasound, and X-ray. MRI can be used to streamline diagnostics and treatment because it does not require patients to be repositioned between scans of different areas of the body. It is even possible to use MRI to visualize, power, and control medical devices inside the human body to access remote locations and perform minimally invasive procedures. Therefore, MR conditional medical devices have the potential to improve a wide variety of medical procedures; this potential is explored in terms of practical considerations pertaining to clinical applications and the MRI environment. Recent advancements in this field are introduced with a review of clinically relevant research in the areas of interventional tools, endovascular microbots, and closed-loop controlled MRI robots. Challenges related to technology and clinical feasibility are discussed, including MRI based propulsion and control, navigation of medical devices through the human body, clinical adoptability, and regulatory issues. The development of MRI-powered medical devices is an emerging field, but the potential clinical impact of these devices is promising.

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This paper has proposed a novel fiber Bragg grating (FBG)-based hybrid displacement and force sensor with a compact structure and excellent resolution by using the transverse property of a tightly suspended and slightly bent optical fiber. The optical fiber, embedded with an FBG element, has been suspended with its ends fixed on the sensor frame and implemented with a pre-tension force by the displacement loading along its vertical direction to form a bent shape. A conversion mechanism has been designed to convert the displacement and force inputs into the transverse movement of different points along the suspended fiber. Experimental results show that the displacement sensitivity and force sensitivity are −219.69 pm/mm within the range of 0–2.5 mm and −345.2 pm/N with a high calculated resolution of 2.9 mN, respectively. Results from both the displacement and force experiments have illustrated a close agreement with values from commercial sensors.

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The objective of this project is to propose an alternative design for hyper-redundant, tendon-driven, discrete-joint manipulators which allows for independent removal of intermediate modules, as well as to conduct a comparative study between two alternative forms of tendon-driven actuation
systems, twisted string actuation and spooling actuation. Hyper-redundant discrete-joint manipulators have individual modules connected in series and when paired with a tendon-driven actuation system, intermediate modules cannot be isolated. This lack of modularity limits the ability to quickly replace intermediate modules without the need to disassemble the entire system. Efficacy of modularity is measured by the fastest time required to remove and add intermediate modules to a series of modules.
Comparison between maximum force generated by twisted string actuation and spooling actuation is done. The effects of different materials and diameter on the maximum force generated for twisted string actuation are also tested. Subjects are able to add and remove intermediate modules from the proposed design faster than a benchmark design. Twisted string actuation tests suggest that it is able to generate a larger force as compared to spooling actuation. Different string material and diameter are
also shown to affect the maximum force generated. If needed,further research should be done to better quantify factors which contribute to failure of the string in twisted string actuation.

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This paper proposes a Modular and Reconfigurable Cable-driven robotic grasper (MoReCa Grasper) for grasping diverse unknown objects in unstructured environments, which integrates the characteristics of full actuation and under-actuation. The mechanical design of this robotic grasper is introduced with a focus on its Lego-like modular design feature and reconfigurable flexible joints. With these features, the length of this robotic grasper can be arbitrarily changed through the addition or removal of the Lego-like finger modules connected by magnets without rerouting or breaking the cables. The shape and degree of freedom (DOF) of the robotic grasper can be adjusted by changing the states of the joints using embedded clutches. When the joints are locked, the grasper can maintain its shape without additional power from actuators leading to better energy efficiency. The kinematics, workspace, and contact force are analyzed. On this basis, an automatically reshaping method (ARM) based on the motor’s current during the operation is proposed. Lastly, an example prototype of the robotic grasper with two fingers (four modules each), is built and tested. In the first experiment, the maximum grasping force is obtained. The second experiment demonstrates the ability of grasping diverse objects via changing the number of the modules and presetting the shape of the robotic grasper. The effectiveness of the ARM is verified in the third experiment.

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Abstract—
THIS paper presents the development of a bidirectional fabric-based soft pneumatic actuator requiring low fluid pressurization for actuation, which is incorporated into a soft robotic gripper to demonstrate its utility. The bidirectional soft fabric-based actuator is able to provide both flexion and extension. Fabrication of the fabric actuators is simple as compared to the steps involved in traditional silicone-based approach. In addition, the fabric actuators are able to generate comparably larger vertical grip resistive force at lower operating pressure than elastomeric actuators and 3D-printed actuators, being able to generate resistive grip force up to 20N at 120 kPa. Five of the bidirectional soft fabric-based actuators are deployed within a five-fingered soft robotic gripper, complete with five casings and a base. It is capable of grasping a variety of objects with maximum width or diameter closer to its bending curvature. A cutting task involved bimanual manipulation was demonstrated successfully with the gripper. To incorporate intelligent control for such a task, a soft force made completely of compliant material was attached to the gripper, which allows determination of whether the cutting task is completed. To the authors’ knowledge, this work is the first study which incorporates two soft robotic grippers for bimanual manipulation with one of the grippers sensorized to provide closed loop control

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